Process of producing electrical heating element



Jan. 4,

E. L. WIEGAND PROCESS OF PRODUCING ELECTRICAL HEATING ELEMENT Original Filed August 31. 1923 Jan. 4, 1927.

- IDWm L. WIIGAND, OI PITTSBURGH, PENNSYLVANIA.

rnoczss or raonucmcnmc'rmcu. maarme ELEMENT.

ori ami application filed August a1, 1923, Serial No.

22, 1985. Serial- No. 8,812.

This invention relates to a process of producing electrical heating elements of the sheathed class, the process and several modifications'of the product being disclosed in my co-pending application Serial No. 660,-

294, filed August 31, 1923, and whereof this application is a division.

The object of the invention is to rovide a process whereby sheathed electrical eating elements of a high quality may beconveniently and expeditiously produced in a very eflicient manner and at a comparatively low cost.

In the drawing, Fig. 1 shows a sheet metal receptacle containing a quantity of impressionable or lastic refractory insulating material, thus i ustrating the results of the first step of the process; Fig. 2 shows a resistor embedded 'within the refractory insulating 'material and illustrates another step inthe process; Fig. 3' shows the results of the next step wherein additional insulat ing material is introduced into the casing; Fig. 4 isillustrative of the step wherein '25 the material, with the resistor embedded therein, is highly compressed; 5 illustrates the drying step; Fig. 6 is i ustrative of the step wherein a cover is applied and the edge wall of the receptacle turned over the periphery of the cover to clamp it in place; Fi 7 shows the "bending step of the process; ig. 8 shows'the step of compress ing the element; and Fig. 9 is a sectional view of an oven with the element therein and is illustrative of the final drying'or baking step. 4

.Inbroa aspect, the imlentiomconsists. in producing a sheathed electrical heating element by placing within a suitable .receptacle a resistor that isenveloped in a mass of refractory insulating material and closin thereceptacle. Then, if the use to whic the element is to be put requires it, the element may be bent to a given shape. Before or after, or in the absence of bending, the

element may be compressed'to. compact the refractor insulating material and render more intimate its contact with all parts of the resistor and sheath. I 4

The process, according to my present preference, is carried out, with optional alternation and omission of certain of the steps, depending upon the character and-- this is a 680,294. Divided and this application fled January manner illustratedin the drawing, by first introducing into a receptacle 1, as shown in F1 1,;a mass of receptive refractory insulating material. designated 2, which may possess some degree of moisture. A class of material found especially. suitable for the purpose is composed of magnesium or aluminum oxide or zirconium silicate, either individually where possible or a compound of them, together when desirable with a binding material such as clay to give the necessary lastieity during fabrication and to effect omogeneity in the final product.

I next emplace within this mass of refractory material a previously formed resistor 3 which may consist of a flat Wire or ribbon of suitable resistance metal'bent into a sinuous or serpentine formation (as will be seen by reference to my application above identified). This step, illustrated by Fig.

2, may be performed by means of the apparatus disclosed and claimed in any of my following .Letters Patent: No. 1,133,347, dated March 30, 1915; No. 1,312,657, dated August 12, 1919; Reissue No. 15,479, dated October 24, 1922, and No. 1,476,126, dated December 4, 192

The third step consists in introducing additional refractory material, designated 2 in Fig. 3, into the receptacle; and, as the fourth step, the material is compressed (Fig. 4) to a greater or less de ree.

In most cases the insnating material, if it be moist is next dried. -This may be acheatingit b directing current through the resistor ig. 5 is illustrative of this step,

' the opposite sides of an electric circuit, represented; by the conductor a and b, being connected to the resistor terminals 3".

The sheath is now completed by closingthe open side of the receptacle as by means of a cover 4 and turning the edges of the side walls of the receptacle inwardly over the mgr in of the cover, this step being il-' lustrate in Fig. 6.

As broizght out in the application whereof ivision, the heating elements disclosed in said application are capable of bein bent into various shapes so as to suit them better to specific purposes. For example, the element may be formed to the contour of an object that is to be heated so that :it may be brought into intimate contact with the object throughout the entire area of its operating face and thus greatly enhance the efiiciency of the element and reduce the operating temperature of the resistor by reason of the more rapid dissipation of the heat.

The bending of the element may be performed as the next step of the process. This step is conventionally illustrated in Fig. 7, where the element is shown as disposed between relatively movable abutments 5 and 6.

A further step, illustrated in Fig. 8, is the compressing of the element. This may be accomplished between the parts 7' and 8 of suitable pressing apparatus.

In some cases there is a final step of baking the element, and this is represented in Fig. 9 where the element is shown in an oven 12.- 4

From the foregoing it will be seen that the process, in its preferred form, comprises all or a part of the following steps:

(a) Introducing into the receptacle a mass of refractory insulating material (b) Embedding the resistor in the material (Fig. 2)

(0) Introducing additional material into the receptacle (Fig. 3)

( (d) lgloderately compressing the material Fig. 4

(e) Df'ying the material (Fig. 5)

(7) Closing the receptacle (Fig. 6)

(g) Bending the element, (Fig. 7

((ih) Compressing the element (Fig. 8); an

(2') Baking the element (Fig. 9).

Regardless of the size, shape and exact nature of the element that is to be produced, the first four steps of the process (as to (i above and represented by Figs. 1 to 4) are preferably but not necessarily performed in the order named. .In most cases thestep (c) of'drying the insulating material (Fig. 5) follows a; then comes the step (f) of closing the receptacle (Fig. 6) and, where the element is not to be bent, the step f is succeeded by the step (it) of compressing the element (Fig. 8), did this, of course, may be followed by thecstep (i) of baking the ele ment if desire With respect to elements of large continuous area, such as those specifically claimed in my co-pending application above identified, and which are to be bent, the bending is done before final compressing. Also, in cases of this kind, where the cover or receptacle are perforated, asin certain modifications shown in my above mentioned applications, the insulating material is left moist until after the closing of the receptacle and the bending of the element, any vapor result ing from the drying of the material escaping through the perforations of the sheath.

In the case ofstrip type heaters and annular type heaters, with their various ramifications, shown and described in the above mentioned application, and in earlier divisions thereof bearing Serial Nos. 697,446, and 757,798, respectively, the element may be and preferably is bent after being other-' wise practically completed. In other words, the insulating material may be dried and the element compressed, and then bent. After being bent, the element may again be compressed if such should be found necessary or desirable.

While I have described quite in detail a desirable form of the invention with certain optional variations, I have also included a broad analysis of the process, and I regard the scope of the invention'as commensurate with this range ofdisclosure.

Having thus described my invention, what I claim is:

1. The process of producing an electrical heating element which comprises the steps of applying in a generally lateral direction to one part of a side opening sheet metal sheath a quantity of granular refractory electrical insulating material and a resistor, securing a complementary part to the former part of the sheath thereby to enclose said insulating material and resistor, and artificially compacting said insulating material.

2. The process of producing an electrical heating element which comprises the steps of applying in a generally lateral direction to one part of a side opening sheet metal sheath a quantity of granular refractory electrical insulating material and a resistor, securing a complementary part to the former part of the sheath thereby to enclose said insulating material and resistor, and compacting said insulating material by subjecting the element to pressure.

3. The process of producing an electrical heating element which comprises the steps of introducing in a lateral direction into a receptacle that is open along one side a quantity of refractory electrical insulating material and a resistor, applying a cover to the receptacle, securing the parts together by turning the edge portion of the peripheral wall of the receptacle over the margin of the cover, and compressing the element.

4. The process of producing an electrical heating element which comprises the steps of introducing into a comparatively shallow sheet metal casing through an open side thereof a quantity of granular refractory insulating material and a resistor, closing the receptacle, and artificially compacting said insulating material.

5. The process of producing an electrical heating element which comprises the steps of introducing into the open side of a relatively shallow sheet metal receptacle, a quantity of granular refractory electrical insulat- Ilu 2 closing the of introducing in a general lprocccs of producing an electrical heating e ement which comprilses the dsteps y ateral lrection into a receptacle that 18 open on one side a quantity of granular refractory electrical insulating material and a resistor, closingthereceptacle, bending the element, and compressing the element. v

8. The process of producing an electrical heating element which comprises the steps of introducing ina lateral direction into a receptacle that is open along one side substantially from end to end a mass of plastic refractory material and a resistor embedded therein, drying the material, closing the. receptacle, and compress the element.

9. Tue rocess of pr iiducing an electrical heating .e ement which comprises the successive steps of introducing in a generall lateral direction .into a receptacle that-1sopen on one. side a mass of impressionable refractory material; embedding a resistor in said material; closing the receptacle, and compressing the element.

10. The process 'of producing an electrical heating element which comprises thesuccessiv'e steps of introducing in a generally lateral direction into areceptacle that is open'on one side a mass of plastic refractory material; embedding a resistor in said material; drying the niaterial; cliising the receptacle, and compressin the element.

11.. The process of pro ucing an electrical heating element which comprises the successive steps of introducing in a generally lateral direction into a receptacle that is open on one side a mass of plastic refractory material; embedding a resistor in said mate rial; drying the material; closing the receptacle; compressing the element, and baking the element.

12. The process of producing an electrical heating element which comprises the successive steps of introducing in a generally lateral direction into a receptacle that is open on one side a mass of moist receptive refractory material; embedding a resistor in .said-material; compacting the material;

drying the same; closing the receptacle;

I and compressing the element;

' 13. The process of roducing an electrical heating element whic comprises the successive steps of introducing in a generally lateral direction a receptacle that is open process of producing anelectrical I terial into the receptacle,

mg said receptacle and compressing said.

' ment.

on one sidea mass of moist receptive .refracmaterial; compacting the material; drying the same; closing the receptacle; and compressingand baking theelement.

14 The process of producing an eldctrical heating element which computes the steps of introducing in a generally lateral directron into a sheet metal receptacle that is open on one side a mass of receptiverefrac- .tory material; embedding a resistor in said material; closing the receptacle; said element to a desired said element, and drying the element.

15'. The process of producing an electrical heating element which comprises thesteps bending of, first, introducing ,ina generally lateral direction intoa sheet metal receptacle that 15 open on one side a mass of impressionable refractory material; second, embeddin a previously formed resistorin said material; third, introducing additional refractory maelement.

16. The process of producing an electrical heating element which comprises the steps of, first," introducing into a sheet metal receptacle a mass of impressionable refractory material; second. embedding a previously 1 formed resistor in saidmaterial; third, in troducing' additional refractory material tory material; embedding a resistor in said shape; compressing V and, fourth, closinto the receptacle; fourth, compressing said material in said receptacle to effect one integral homogeneous mass with the resistor completely encased therein, and fifth, closing said receptacle and compressing said ele- 17. The process of producing an electrical heating'element which comprises the steps of, first, introducing into a. sheet metal receptacle a mass of moist impressionable refractory'material; second, embedding a previously formed resistor in 'said material; third, introducing additional refractory material into the receptacle; fourth, compressing'said material in said receptacle to effect one integral homogeneous mass with theresistor completely encased therein; fifth drying the material; and sixth, closing said receptacle and compressing said element.

Ilu

18, The process of producin n cal heating element which comprises the step of, first, introducing into a sheet metal receptacle a mass of impressionable refractory material; second, embedding a previously formed resistor in said material; third, in-" troducing additional refractory material into the receptacle; fourth, compressing said material'in said receptacle to effect one integral homogeneous mass with the resistor completely encased therein; fifth',- closing said 're'ce tacle and compressing the'iilement; and sixt baking the element thus formed,

19. The process of producing-an electrical heating element which comprises the steps of, first, introducing into a sheet metal receptacle a mass of receptive refractor material; second, embedding a prev1ously formed resistor in said material; third, introducing additional refractory material into the receptacle; fourth, compressing the said material in said receptacle; fifth, closing said receptacle; and sixth, bending said element to any desired shape and compressing said element.

20. The process of producing an electrical heating element which comprises the steps of, first, introducing into a sheet metal receptacle a mass of'receptive refractory material; second, embedding a previously formed resistor in said material; third, introducing additional refractory material into the receptacle; fourth, compressing said material in said receptacle; fifth, closing 'said receptacle; sixth, bending said element to a desired shape and compressing said element, and seventh, drying said element.

21. The process of producing an electrical heating element which comprises the steps of, first, introducing into a sheet metal receptacle a mass of plastic refractory material; second, embedding a previously'formed resistor in said material; third, introducing additional refractory material into the, receptacle; fourth, com rcssing said material .in said receptacle; fi th, drying said material, and sixth, closing said receptacle and compressing said element.

In testimony whereof, I hereunto afiix my signature.

EDWIN L. WIEGAND.

DISCLAIMER 1,613,426.-Edwin L. 'Wiegand, Pittsburgh, Pa. PROCESS or PRODUCING ELECTRICAL HEATING ELEMENT. Patent dated January 4, 1927. Disclaimer filed November 2, 1938, by the patentee; and the licensee, Edwin L. Wt'egand Company. Hereby enter this disclaimer: v

A. To so much of laim 2 of said Letters Patent as may cover any process except for producing an extended-resistor sheet-metal-sheathed electrical heating element relatively thin and wide in cross section and having the resistor embedded in granular refractory electrical insulating material, or any process unless using a part that is relatively shallow channel shape in cross section, binder-containing electrical insulating material at least part of which is unintegrated and has the binder thereof unset, a resistor that is a resistance conductor arranged in a formation correspondingly relatively thin and wide in cross section, and a complementary part that is sheet metal, or any process except a process in which the quantity of electrical insulating material is applied through the open face of the part, securing the complementary part completes a sheet metal sheath relatively thin and wide in cross section enclosing the insulating material and the resistor, the pressure is in a direction generally perpendicular to the major cross-sectional dimension of the element, and subjecting the element to pressure re-forms the unintegrated material and forms the entire material into a compact mass embedding the resistor and in heat-conduction contact both with all parts of the surface of the conductor over substantially the entire length of the conductor and with all parts of the interior of the sheath over all parts of the exterior of the mass, or any process except for producing an element that subsequently is heated to set the unset binder.

B. To so much of claim 5 of said Letters Patent as may cover any process except:

The process of producing an extended-resistor sheet-metal-sheathed electrical heating element relatively thin and wide in cross section and having the resistor embedded in granular refractory electrical insulating material, which comprises the steps of introducing into the open side of a relatively shallow sheet metal receptacle, a quantity of granular refractory electrical insulating material and a resistor composed of a resistance conductor arranged in a formation correspondingly relatively thin and wide in cross section, at least part of said material being unintegrated, closing the open side of the receptacle by adding a complementary sheet metal part completing a sheet metal sheath relatively thin and wide in cross section enclosing the resistor and the material, and compressing the element in a direction generally perpendicular to the major cross-sectional dimension thereof re-forming the unintegrated material and forming the entire material into a compact mass embedding the resistor and in heat,- conduction contact both with all parts of the surface of the conductor over substantially the entire length of the conductor and with all parts of the interior of the sheath over all parts of the exterior of the mass. 7

C. To so much of claim 9 of said Letters Patent as may cover any process except: The process of producing an extended-resistor sheet-metal-sheathed electrical heating element relatively thin and wide in cross section and having the resistorembedded in granular refractory electrical insulating material, which comprises the successive steps of introducing in a generally lateral direction into a relatively shallow sheet metal receptacle that is open on one side, through the open face thereof a mass of impressionable unintegrated granular refractory electrical insulating material containing unset binder; embedding a resistor in said material, said resistor be ng arranged in a formation correspondingllf relatively thin and wide in cross section; closing the receptacle by adding a com ementary sheet metal part completing a sheet metal sheath relatively thin and wide in cross section enclosing the resistor and the mater al, and compressing the element in a direction generally perpendicular to the ma or cross-sectional dimension thereof re-formmg the unintegrated material, and heating the element and setting the unset binder.

[Oficial Gazette December 6, 1938.] 

